The following figure shows a top-down structure diagram for an OpenEdge application that calls shared library functions.

The dotted boxes emphasize that although shared library functions are called from within an OpenEdge application, they actually reside in external shared libraries.

An OpenEdge application can access a shared library function much like an internal ABL procedure. The client declares the function and its file using a PROCEDURE statement, defining all function parameters with DEFINE PARAMETER statements. ABL provides a special set of parameter data types to match C and Windows data types, and a set of statements and functions to build and access C structures from ABL. The client executes the shared library function exactly like an ABL procedure, using the RUN statement.